1. Field of the Invention
The present invention relates to an adjustable handlebar stem for bicycles and the like. More particularly, the present invention relates to parallelogram type linkage between the handle bars and the stem to permit adjustment of the position of the handle bars and a locking means for locking the upper and lower links in a fixed and stable position.
2. Prior Art
Bicycling for long distances can be uncomfortable because the rider must sit in the same position for extended periods of time. In addition, for riders with health problems, such as arthritis, bicycling for even short distances can become uncomfortable. Although bicycle components and configurations are typically adjustable, the adjustments require tools and the adjusted position is permanent for all practical purposes. For example, the stem and the seat may typically be adjusted vertically and the handle bars and seat rotate forward and back by loosening a bolt and clamp with a set of wrenches. These adjustments are usually made to accommodate the physical build of the intended user and are not readjusted. The difficulty in making the adjustments makes frequent changes to suit comfort unpractical. For example, a rider will not usually stop, dismount, obtain tools, loosen a component, adjust the component, tighten the component, put away the tools, and continue riding every time the rider feels uncomfortable.
In addition, many bicycle components and configurations are intended for specific purposes. For example, racing and mountain bicycles often have handle bars that are positioned low and forward with respect to the bicycle and away from the rider. Touring bicycles often have handle bars positioned high and back with respect to the bicycle and towards the rider. These components and configurations take advantage of efficiencies inherent in the rider's posture. A rider positioned low and forward is more suited to racing or climbing while a rider positioned high and back is more suited to touring. While many riders are dedicated enough to a particular type of riding, such as racing, to own a bicycle specifically designed for that purpose, others own a single bicycle that is used for all purposes, such as mountain biking, touring, and racing. Because a rider lacks the dedication to any particular type of riding, or perhaps lacks the funds to own several bicycles, the rider must settle on one style of bicycle and use it, with the inherent inefficiencies, for all types of riding.
Furthermore, all types of riders encounter various riding conditions that may alter the preferred posture of the rider. For example, while climbing or riding at high speed, the rider may wish to be positioned low and forward. But as traffic is encountered, the rider may prefer to be positioned high and back.
U.S. Pat. No. 5,138,900 issued on Aug. 18, 1992 to Hals discloses a quadrilateral type linkage between the handlebars and the stem to allow the handlebars to be adjusted between a low and forward position to a higher and back position. The position of the handlebars is fixed by a wheel hub quick-clamp mechanism disposed on an upper link engaging a groove formed in a lower link. Thus, the upper and lower links are essentially clamped together and held by friction. One problem with this method for positioning the handlebars is that the friction type connection between the upper and lower links may be overcome by a large force causing an abrupt change in the handlebar position. An abrupt change in the handlebar position may cause the rider to lose balance or control. In other words, if the rider exerts a large force on the handlebars, as when the rider hits a bump or dip, the friction connection between the links may loosen and cause the position of the handlebars to adjust abruptly. This abrupt change may cause the rider to lose control, injuring himself and damaging the bicycle.
Alternatively, Hals discloses a cable operated conical plunger disposed in the upper link and engaging a conical recess formed in the lower link to fix the position of the handlebars. One problem with this method of fixing the handlebar position is that the tapper or conical shape of the plunger and recess may enable the plunger to slip from the recess when a large force is exerted on the handlebars. Furthermore, the cable system adds complexity and provides an additional area for possible failure.
U.S. Pat. No. 5,273,302 issued on Dec. 28, 1993 to Ureel discloses a parallelogram type linkage between the handlebars and the stem to allow the handlebars to change positions. The position of the handlebars is fixed by a pin disposed in a handlebar member engaging radially extending slots formed in the end of one of the links, like a toothed gear. One problem with this method of positioning the handlebar is that the link attached to the toothed gear acts as the long arm of a lever. Force applied to the mechanism is multiplied by the length of the link, thus tending to cause an excessive force and risk of failure at the teeth of the gear.
Another problem with both the Hals and Ureel devices is their structure. The linkage structures disclosed by Hals and Ureel are loose and unstable. For proper control and feel, bicycling requires that the structure of the bicycle be firm and solid. In addition, for some types of bicycling, such as mountain biking, the structure must have great strength. Furthermore, the bulk of the structures does not lend themselves to the streamline, efficient, light-weight style of bicycling.
Therefore, it would be advantageous to develop an apparatus for adjusting the position of the handlebars to adapt the bicycle to the riding conditions encountered and to change the riders posture for comfort. It would also be advantageous to develop and apparatus for easily adjusting the position of the handlebars while riding. It would also be advantageous to develop and apparatus for adjusting the position of the handlebars of a bicycle while maintaining control and the firm and solid feel of the bicycle and maintaining the efficient, lightweight style of bicycling.